Optimization and characterization of a ZnO biosensor array

Practical usage of acoustic biosensors has revealed that high quality factor, Q, is an important attribute of a highly sensitive acoustic sensor. In this research, we present performance optimization of ZnO thin-film bulk acoustic resonators (FBARs) operating in the thickness shear mode through characterization of a variety of electrode geometries. The resulting average Q and K2 from each of the electrode geometries were calculated and compared. Based on these results, a preferred electrode configuration was selected, and fabricated into an 8-device array. The arrays were tested in physiologically relevant environments to illustrate the effects of temperature and solution conductivity on the stability of the resonators. The devices demonstrated a temperature coefficient of frequency of ∼25 ppm/°C. The resonators also exhibited reasonable stability under varying levels of solution conductivity as tested by exposing the devices to solutions containing a varied amount of NaCl in deionized H2O.